Statistical rate theory description of beam-dosing adsorption kinetics

Abstract

Absolute rate theory and the sticking probability approach have been previously examined as possible means of predicting the rate of adsorption. However, when applied to examine adsorption kinetics, they have been found not to contain the coverage and pressure dependence required for several important systems including CO–Ni(111). Statistical rate theory (SRT) is being developed with the objective of predicting the rate of molecular (or atomic) transport across the interface between macroscopic phases in terms of experimentally controllable variables and material properties of the two phases. Previous applications of SRT to adsorption have been limited to systems for which both the gas phase pressure and the temperature could be assumed to be constant. Herein, the SRT approach is extended to systems in which the number of molecules in the system (and hence the gas phase pressure) is not constant. To examine this extension, SRT is used to formulate the equations governing the rate of adsorption in isothermal, beam-dosing experiments. These equations are then combined with the values of certain material properties that have previously been established and a hypothesis that the value of the equilibrium adsorption cross section is given by the area of an adsorption site. The kinetic data for CO adsorbing on Ni(111) data reported by three different laboratories are then examined. For each set of experimental data, constants had to be inferred that were related to the experimental apparatus used and as such they were not expected to have any coverage or pressure dependence. The good agreement found between the predicted and measured adsorption kinetics indicates that all of the necessary coverage and pressure dependence was explicitly predicted from the SRT approach.

Theoretical description of the kinetics of solute adsorption at heterogeneous solid/solution interfaces

“…the rate of exchange at the liquid/gas interface [17][18][19], hydrogen adsorption by metals [20], electron exchange between ionic isotopes in solution [21], permeation of ionic channels in biological membranes [22], and rate of liquid evaporation [23][24][25]. Ward and co-workers were the first to show how the SRT approach can be applied to describe the kinetics of isothermal adsorption at the gas/solid interfaces [26][27][28][29], and the kinetics of thermodesorption [30]. Then a series of papers has been published during the last decade by Rudzinski and co-workers, showing how that new description can be generalized further to describe the kinetics of isothermal gas adsorption/desorption on/from energetically heterogeneous surfaces [31][32][33][34][35] as well as the kinetics of thermodesorption [36][37][38][39].…”

Effects of nonlinear interfacial kinetics and interfacial thermal resistance in planar solidification

“…At present, it is unclear what assumptions should be made in describing the interface during solidification. Using a planar solidification model, we consider three possibilities: (1) temperature equality and linear kinetics, (2) a nonlinear kinetics relation obtained from statistical rate theory [24][25][26][27] and temperature equality, and (3) nonlinear kinetics and temperature discontinuity. The nonlinear kinetics employed allows for a temperature discontinuity and does not contain any new fitting parameters.…”

Liquid-Vapour Phase Change Rates and Interfacial Entropy Production

“…When compared with measurements, close agreement was found over a range of coverages [29]. This expression for the chemical potential was also used with SRT to examine beam-dosing adsorption kinetics [10), but certain apparatus constants were not given with the measurements. Although the calculations were in close agreement with the measurements, it was only concluded that the SRT expression for the adsorption rate gave explicitly the coverage dependence and was consistent with the measurements.…”